Chemical reaction control



Patented Mar. 10, 1942 d UNITED STATES PATENT OFFICE 2,276,120 cnE rcAr.REACTION CONTROL Charles L. Thomas, Chicago, 11]., asslgnor to UnlversaiOil Products Company, Chicago, Ill., a I corporation of Delaware NDrawing. Application July 8, 1940,

Serial No. 344,374

8 Claims. (Cl. 23-1) This invention relates to improved media usetioncomprise heat exchange media consisting ful as heat exchange materialsand is a continuof mixtures of stannous chloride with an anation-in-partof my co-pending application Serial hydrous metal halide, said mixturehaving a No. 274,976, filed May 22, 1939. More particumelting pointbelow that at which the reaction larly it relates to a material usefulin catalytic in which it is to be used occurs and preferably reactionsfor the storing and utilization of the below 450 C., said mixtures beingparticularly heat evolved in an exothermic reaction for use in usefulfor removing heat during an exothermic carrying out endothermicreactions. The invenreaction and using said heat in an endothermic tionrelates especially to the use of a low meltreaction. ing mixturecomprising metal halides. l0 The mixtures used in the present inventionand The invention is particularly useful when emwhich may compriseeutectics aswell as other mixployed in connection with reactions whereinthe V tures should desirably have the following charexothermic reactionand the endothermic reacacteristics:

tion are of the same order of magnitude insofar 1) A low melting pointwhereby they can be I as heat evolution and consumption are concemed,maintained in the liquid state at relatively low and wherein thetemperatures at which these retemperatures when not in actual use. Ifthe actions take place are within the same approximelting point is toohigh, difficulties may arise mate range. either in pumping or inotherwise handling, due

Among the types of processes in which the to freezing. The melting pointmust necessaripresent invention is usefully employed are cata- 1y bewell below the temperature at which they lytic cracking, catalyticdehydrogenation, cyclizaare used. tion of aliphatic hydrocarbons, etc.All of these (2) The salt mixture should be thermally stable reactionsare endothermic in character and durat any temperature which is likelyto be reached ing the course of the conversions are accompaduring thecourse of the reaction. Normally this nied by the deposition ofnon-volatile carbonaceincludes temperatures up to 600 C. or higher. ousmaterial on the catalytic masses used to asv (3) They should be stablein contact with air sist the conversion. It is common practice to reorminor amounts of moisture, and should not move the carbonaceous depositsfrom the catalyst form high melting. products in contact with thesesurfaces by heating the catalytic masses at temmaterials at ordinary orelevated temperatures peratures in excess of 500 C. in the presence offor long periods of time. oxygen-containing gases, whereby the carbon is(4) The mixtures should be non-corrosive oxidized to carbon monoxide andcarbon dioxide. to ordinary steel or ferro-alloy equipment. This Thisreaction is accompanied by an evolution of is, of course, essential bothfrom the standpoint heat which must be conducted from the system of theequipment involved, and loss of chemicals to prevent damage to both theequipment and which might occur due to failure of the equipthe catalystmasses. In many cases, the heat ment during the process.

evolved during this reactivation step is suflicient (5) The constituentsshould not react with or nearly suflicient to supply that, required forexplosive violence with hydrocarbons in case of the processing step.Normally in carrying out' accidental contact therewith such as.might beyt c p o se of his type,'the processi g 40 caused by failure of theequipment, or due to and reactiv ion st ps e arried out alternatelycontamination of the salt mixture with organic in the form of a cyclewherein the processing rematerials under any circumstances.

action is carried out for a definite i d of tim (6) The constituents ofthe mixture should be and the reactivation step is carried, out foranother definite period of time, which may be the. to plicate so thatthe reactivation step is carried out. is; ifi g g ggf fggfiz gfig g gqgsg' 2 2:1;1:: e s:assessments: e; t r be maintain other types ofoperation, the cycle is carried out the mammal m Substantlauy hquld formrelatively inexpensive.

I (8) The material should have high specific m a single reactor, whereinthe process period I I and regeneration period are alternated at regul"glvmg 8 e t age capac1 y. h

lar intervals; degree of heat conductivity.

In one specific embodiment the present inven- (9) It should berelatively non-poisonous and (7) The boiling'point should be well above.the

non-corrosive to the skin so that it does not introduce undue hazardsduring handling.

An example of materials of this nature is stannous and zinc chloride inthe quantities of 56.1 mol and 43.9 mol respectively, having a meltingpoint of 171 C. Another example is stannous chloride, 78.3 mol andcuprous chloride 21.? mol having a melting point of 171.7 C. Obviously,the melting points of the combinations will vary with the materials usedand with the proportions used, the above combinations being given forillustration only. The melting points can be varied still further by theaddition of a third component, and the use of stannous chloride with twoor more added metal halides is included within the scope of theinvention. Although it is preferred to employ mixtures having meltingpoints below approximately 450 C., any mixture melting substantiallybelow the temperatures at which the various reactions in which it is tobe used occurs maybe used.

The relatively low melting points of thesemixtures permit their beingmaintained in liquid form by moderate heating, and in many cases highpressure steam is suflicient so that the danger of freezing of lines,and solidification of the salt in pumps and other parts of the equipmentis minimized by the relatively simple procedure of jacketing the partscontaining the molten salt and circulating a heated medium.

The apparatus which may be used is not a special feature of theinvention, but may comprise any suitable type of equipment wherein acatalytic reaction involving an endothermic reaction may be carried outsimultaneously with the carrying out of an exothermic reaction, andpermitting the transfer of heat through the medium of a molten salt fromone to the other. This may comprise separate reactors which are operatedin cycles of alternating periods, and wherein the molten salt surroundsthe tubes of chambers wherein the catalyst is disposed, means beingprovided for the pumping of the molten salt from a region of hightemperature to a region of lower temperature, and vice versa. In anothertype of equipment, the reactor may comprise a multiplicity of tubescontaining catalytic masses, the tubes being arranged so that a part arein the process stage while the remainder are in the reactivation stage.The heat exchange medium surrounds the tubes and is circulated bymechanical means. Another type of reactor may employ chambers, normallyoperated in pairs, wherein the catalyst mass is disposed. The heatexchange medium is circulated through tubes passing through the catalystbed, and the molten salt from one reactor to another. Additional heatmay be supplied or removed from the heat exchange medium by passage of aportion of the molten salt through heaters or coolers as may be desired.

Although the mixtures described herein are particularly useful inconnection with catalytic reactions, it is intended that they shall beused as thermophoric materials generally.

I claim as my invention:

1. In a process for utilizing the heat evolved during an exothermicreaction for carrying out an endothermic reaction by using a heatexchange medium, the improvement which comprises using a mixture ofstannous chloride with an anhydrous metallic halide, said mixturemelting below 1000 C.

2. In processes for using the heat of reaction in an exothermic reactionto supply the heat for an endothermic reaction, the improvementcomprising using a binary mixture of stannous chloride and an anhydrousmetal halide as the heat carrying material, said mixture melting below1000 C.

3. In processes for using the heat of reaction in an exothermic reactionoccurring at a temperature in excess of 500 C. to supply the heat for anendothermic catalytic reaction occurring at a temperature in excess of450 C., the improvement comprising the use of a mixture of stannouschloride with an anhydrous metallic halide, said mixture having amelting point below 450 C. as a heat exchange medium.

4. In processes for utilizing the heat of reaction from an exothermicreaction occurring at a temperature in excess of about 500 C. forcarrying out a reaction occurring at a temperature in excess of about450 C., the improvement which comprises the use of a mixture of stannouschloride and anhydrous metallic halides, said mixture having a meltingpoint below 450 C., as a heat exchange medium. I

5. In a process for utilizing the heat evolved during the reactivationof a carbonized catalytic mass for carrying out an endothermic catalyticreaction, the improvement which comprises using a mixture of stannouschloride and an anhydrous metallic halide as a heat carryingmedium,'said mixturemelting below 450 C.

6. The porcess of claim 1 wherein the mixture of salts is a eutecticmixture.

7.'The process of claim 1 further characterized by using a mixture ofstannous chloride and an anhydrous bi-valent metallic halide.

8. In processes for using the heat of reaction of an exothermic reactionto supply the heat for an endothermic change cccurring at a temperaturesubstantially below said exothermic reaction, the improvement comprisingthe use of a mixture of stannous chloride with an anhydrous metallichalide as a heat exchange medium, said mixture melting below thetemperature at which said endothermic change occurs.

CHARLES L. THOMAS.

